1. Field of the Invention
This invention relates to biodegradable acid derivatives and to the use of such derivatives as highly stable hard water soaps and to liquid and solid detergent compositions containing such derivatives. More specifically, this invention relates to detergents having as the essential ingredient a water-soluble beta- to epsilon-substituted alkanoic acid derivative.
2. Description of Prior Art
It is known in the art to use alkali metal salts of naturally occurring fatty acids, such as sodium salts, as soaps (G. B. No. 1,167,826). Such soaps, while effective detergents under soft water conditions, form precipitates due to the presence of such ions as calcium, magnesium or iron. These precipitates may contribute to the formation of rings around sinks or bathtubs. The detergent ability of any remaining soap in solution is considerably lessened. Other additives are usually added to such detergent compositions to increase both ionic strength for improved solubility and cleaning ability, including such additives as "builders". The commonly used builders are the sodium phosphate and nitrilotriacetate salts. The use of phosphates in detergent and soap compositions are under considerable criticism because they constitute pollutants in rivers and streams. The effect of the nitrilotriacetate salts in natural water courses is presently being reviewed.
Another class of soap is the alkyl benzene sulfonate, having an alkyl group of up to about C.sub.20. In U.S. Pat. No. 3,296,146, an alkyl benzene sulfonate soap is stated to have improved detergency by the presence of a 2-hydroxyl-1-amino alkane. In U.S. Pat. No. 3,320,174, there is disclosed a detergent composition containing linear alkyl benzene sulfonates, which may also contain other additives, such as lauric diethanolamide or its ethylene oxide derivatives. The difficulty with these benzene sulfonates is that, although they are somewhat biodegradable, they are relatively slower to decompose, possibly because of the benzene ring which is difficult to break down by microbial attack. Moreover, they often require the use of phosphate or nitriloacetate builders for improved detergency. U.S. Pat. No. 3,305,488 describes detergent compositions containing an organic detergent and an alkali metal or ammonium salt of 10-hydroxystearic acid. In combination with synthetic detergents, such as alkyl benzene sulfonates, or derivatives of fatty acids, such as sodium sulfate glyceryl monoesters of fatty acids, these salts are said to improve detergency performance. But the salts are stated to be poor detergents alone in comparison with ordinary stearic acid soaps (col. 3, lines 2.5).